With the wide availability of GPS sensors in modern devices (e.g., smartphones) and readily available location services on major smartphone platforms, location-awareness has become a common feature of both business and consumer applications. These services typically provides reliable results when the device is outdoors and unreliable results when the device is indoors. For better indoor tracking, a Wi-Fi infrastructure or a Bluetooth infrastructure may be leveraged. In some cases, the infrastructure may still not provide reliable indoor tracking (e.g., a building may have a few Wi-Fi access points that provide little coverage throughout the building).